The MAC-10, abbreviation of Military Armament Corporation Model 10, is a recoil operated sub-machine gun (technically, a "machine pistol") developed in the United States from the 1960s to 1980s. The gun was originally designed for use by police forces, and even saw limited service in the Vietnam War, however it was soon proven that such a small gun cannot accurately fire beyond 20 meters at such a high rate of fire. Its manufacture continued until 1986 when post-dated fully automatic firearms were banned for civilian ownership, and no government agencies showed interest. The MAC-10 achieved success through Hollywood rather than real life, because few of the guns ever made it into the hands of criminals, and even then were marginally effective. The Mac-10 is similar to the TEC-9 only that it has faster rate of fire. In GTA Vice City and Liberty City Stories , the Mac-10 has an unbelievable fast rate of fire and can shoot up to 30 rounds in five seconds, in fact it is faster than the Micro Uzi or Micro SMG . In GTA Vice City Stories , the silencer has slowed down the Mac-10's rate of fire and thus it's not able to fire as many rounds at a limited amount of time as it's predecessor.
Typically, no one uses the Mac-10 in Grand Theft Auto: Vice City, except for the Ammu-Nation owner in Ocean Beach. When aimed a gun at, he uses a Mac-10. The shots don't take a lot of damage, but they fire fast.
In Liberty City Stories, the mission, Sindacco Sabotage, the Leones and the Diablos use this gun for their gang war. This is the only time that this gun is wielded by NPC hands.
In Vice City Stories, the Silenced Mac-10 is used by the Sharks or your illegal gang members to defend themselves.
The Mac from GTA Vice City and Liberty City Stories.
The weapon was originally supposed to have a silencer in Grand Theft Auto: Vice City. The silenced version can be seen on the game's official website. Text strings in the game files also refer to the weapon as SilencedIngram.
As the Vice City HUD suggests, the Micro Uzi from GTA III was going to return in Vice City. But it was cut.
Real life version of MAC-10 comes with two different calibers: .45 ACP and 9x19mm Parabellum, but since every other sub-machine guns in game uses same ammo as MAC-10 (Tec-9, Uzi, MP5, all 9x19mm caliber [although Uzi can use .45 ACP too]), the MAC-10 in game uses 9x19mm Parabellum.